Specification Update

Errata

AT63. BTM/BTS Branch-From Instruction Address May be Incorrect for Software

Interrupts

Problem: When BTM (Branch Trace Message) or BTS (Branch Trace Store) is enabled, a software

interrupt may result in the overwriting of BTM/BTS branch-from instruction address by

the LBR (Last Branch Record) branch-from instruction address.

Implication: A BTM/BTS branch-from instruction address may get corrupted for software interrupts.

Workaround: None identified.

Status: For the steppings affected, see the Summary Tables of Changes.

AT64. Performance Monitor SSE Retired Instructions May Return Incorrect

Values

Problem:

The SIMD_INST_RETIRED (Event: C7H) is used to track retired SSE instructions. Due

to this erratum, the processor may inaccurately count certain types of instructions

resulting in values higher than the number of actual retired SSE instructions.

Implication: The event monitor instruction SIMD_INST_RETIRED may report count higher than

expected.

Workaround: None identified.

Status: For the steppings affected, see the Summary Tables of Changes.

AT65. REP Store Instructions in a Specific Situation may cause the

Processor to Hang

Problem: During a series of REP (repeat) store instructions a store may try to dispatch

to memory prior to the actual completion of the instruction. This behavior

depends on the execution order of the instructions, the timing of a

speculative jump and the timing of an uncacheable memory store. All types

of REP store instructions are affected by this erratum.

Implication: When this erratum occurs, the processor may live lock and/or result in a

system hang.

Workaround: It is possible for BIOS to contain a workaround for this erratum.

Status: For the steppings affected, see the Summary Tables of Changes.